How could you rely on a signed message now ? cause if it was sold back in august then the new owner was already signing through all of his keys constantly.
even priv. keys might have been sold and if someone signs then there is nothing that can prove that it's master-P or not.

though If something proves that the account was sold and with all under original master-P's control then he is definitely not trustworthy. He must have know that there could be a major scam with his account when in hands of the new buyer.

However i think there is more to it and concluding anything might not be appropriate but i just hope that the victim's receive their funds back.